Title: DNA Responses in Wild-derived Mice A central scientific question of this proposal is understanding the mechanism of host responses to cytosolic DNA using genetic approach. We used evolutionary divergent wild derived mice of MOLF strain to map, identify and characterize novel mutations at the N-terminal domain (NTD) of STING, one of the main DNA-sensors and mediator of responses to DNA. These mutations confer low production of IFN in MOLF macrophages. Despite defective IFN-production, MOLF exhibit high levels of IL6 in response to DNA thus revealing the complexity of STING-mediated responses. The novelty of these studies in that i) they highlight for the first time functional importance of NTD of STING while recent studies focused exclusively on the C-terminal region of STING; ii) they describe novel model of DNA-response that is polarized from IFN towards other cytokines; iii) they show that the mutant allele is inherited in a dominant manner thus alluding to a possible mechanism of STING- mediated signal transduction; iv) they present evidence of other (novel) sensors of DNA that could be identified via unbiased genetic approach. Accordingly, our 2-aim plan addresses characterization of the mutant STING allele (Aim 1) and identification of other loci conferring DNA-responses in MOLF mice (Aim 2). Together, the Aims provide a comprehensive analysis of DNA responses in MOLF. Given our expertise and track record in mapping and positional cloning as well as broad knowledge of mechanisms of activation of innate immune responses, it is likely that we will find novel components of cytosolic DNA sensing pathway(s), which is very important in protection of the host against viruses and bacteria. Thus, the scientific impact of this proposal is defined by a possibility of identification of novel components regulating responses to host- and pathogen- derived DNA. Most importantly, the identification of these genes will be insightful for translational research relevant to human health. ! !